Server or system virtualization is a technology that enables partitioning of a physical machine into several equivalent virtual machines capable of hosting independent operating system instances. Several server virtualization capabilities such as virtual resource management, automated provisioning capability and live migration are worthy of taking note in this context.
A virtualized infrastructure provides an optimized operating environment that is malleable to suit varying demands Service providers who host applications and servers for their customers use grid technology to implement an optimized multi-tenant hosting environment. More crucially, guaranteeing Quality of Service (QoS) and consequently adhering to the Service Level Agreement (SLA) for these applications is even more challenging. Besides the load balancing, monitoring, scheduling and resource allocation capabilities of grid solutions, there is need for powerful provisioning, resource management, application level monitoring and SLA conformance mechanisms.
Transient load surges and global synchronization of peak load on certain classes of applications causes them to perform poorly, which in effect, adversely affects the QoS guarantees. Grid schedulers do very little to manage the application on a continuous basis. This is where live migration capability of virtualization can come in handy. If an application is wrapped as a VM and is scheduled as such instead of being allocated directly to the PM, live migration capabilities of virtualization technologies can be leveraged to move out the application to a location, where there is a higher likelihood of QoS conformance.
There have been attempts to address application QoS service issues on virtualized environment, whereby these solutions migrate the applications to lesser-utilized servers whenever there is a sustained breach in application's QoS. This phenomenon is termed as ‘event-based’ migration. While ‘event-based’ migration helps at solving the issue in the near term, it could easily lead to sub-optimal allocation, which in turn can cause a slew of migration activity.